Electrical measuring instrument.



L. W- CHUBB. ELECTRICAL MEASURING INSTRUMENT.

APPLICATION men JAN. 2. m5.

mm Nov 28, mm

WITNESSE3:

The plugs ceptacles 18 and 21 that correspond to the isnioved to the contact member 6 that is marked 6, these together corresponding to the temperature of the thermal junction 11.

17 and 20 are inserted in the retemperature of the air as indicated by the thermometer 10. In this instance. we may assume this reading to be 24, for purposes of explanation. The switch 15 correspoiuling to the thermal junction 11 is depressed and the lower junctions of the thermocouples 1 are heated, by any of the well known means, to such a temperature that the galvanometer 16 shows no deflection. This indicates that the hot and cold junctions of the thermo-couples 1 are oi the correct difference in temperature to cause the instrument to have electric force.

After the device is adjusted, if it is desired to determine the temperature of any of the junctions 14, the corresponding switch 15 is depressed to connect the galvanometer 16 in circuit, and the movable contact members 7 and 8 are adjusted until no current traverses the galvanometer 1G. I l. as we have assumed, the plugs 17 and 2() are inserted in the receptacles 1S and 21 come sponding to the indication of the thermometer 10, the movable contact members 7 and 8 will then indicate directly the temperature of the junction 14.

The principle of operation of my invent'ion is similar to that of the operation of an ordinary potentiometer with the exception that, instead of providing the potention'ieter circuit with a potential due to an RI drop along a. resistor, I provide a potentiometer circuit with a potential due to a thermoelectric force. The cold junction 5) and the hot junctions 11 or 14 are so connected to the potentiometer circuit that, when no current traverses the galvanomcter 16, it indicates that the two circuits are of the same potential and in opposition. Thus, it the potenq tial of the thermo-couples of groups 2 and 3 are known and,

since in certain well known lZl'IQI'IHO-COHPlQS these differences in. potential are prop'ortiol'ial to the difference in temperature between the hot and cold junctions of the thermo-couples 1, an accurate indication of the difference in temperature between the cold junction 9 and thehot junctions 11 or 14 may be obtained.

In'order to cause the device to indicate the actual temperature and not temperature increased temperature of the air. Thisis automatically taken care of by the plugs 17 and 20 when they are inserted in the proper receptacles 18 and 21, corresponding to the air temperature when the the correct counter thermo-- to constitute a device is being adjusted. Thus. instead of determining the temperature dill'erencc between the hot and cold junctions 9 and 1l-, the actual temperature oi the junction H is obtained.

The unctions 14- may be omitted and the device may be used for determining the value of small sources of electromotive forces. This may be done by comparing the thermo-electromotive force to the source of potential to be determined. as is done in any ordinary potentiometer. Further. instead of adjusting the device by the use of a thermocouple. a standard cell may be employed or an ordinary potentiometer may be adjusted by the use of standard junctions fl and 11, in lieu of a standard cell.

It will be understood that the thermocouples are constructed of two dissimilar metals and that the conductors leading from the' couples are of the same metal as those parts of the couple to which they are connected. That is, for purpc es of explanation, the junction 9 may be imposed of an iron strip 22. and a nickel-copper alloy strip 23. This nickel-copper alloy strip extends to a nickel-copper strip 24 that comprises a part of the junction 11. The iron strip 22 extends to the plug 17. The conductors 4- may be of iron and they are connected to the iron strips constituting parts of the thermocouples 1. It must be understood that my invention is not limited to iron and nickel copper alloys. but this was used merely to show how the junctions formed complete couples, as it is thcrnm-couple must compris a hot and a cold junction.

Although I have shown and described a potentiometer having specific connections, it is evident that various mmlilications oi the connections may be etl'ected within the spirit of my invention. and l desire that such n'iodifications shall be included within its scope.

I claim as my invention:

1. A measuring instrument comprising a plurality of thermo-(mmles so arranged US to constitute a mtentiometer conductor having a plurahty ot equal-potential sections.

2. A measuring instrument comprising a plurality of thermo-coiiples so arranged as potentiometer conductor.

3. A measuring instrun'lent comprising a plurality of thermo-couples arranged to constitute a.potentiometer conductor and means for comparing therewith the potential of an unknown source of potential.

4. A potention'leter con'iprising a. potcntiometer conductor and a. thermocouple having a thermometer adjacent thcrcto, said thermo-couplc being so arranged as to determine the drop in potential along the said poten ti 011101101 conductor.

along the said thermo-electric potentiometerconductor.

6. In an electrical measuring instrument, the comlunation with a thermo-electr1c source of potential constituting a potentiometer conductor, of means for comparing an electromotive force of an unknown value with the potentiometer conductor to determine the value of the sames 7. A potentiometer comprising a thermoelectric potentiometer conductor, an electroresponsive device and means for so connecting a source of electromotive force of unknown value to such part of said potentiometer conductor and to the electro-responsive device that no current traverses the said electro-responsive device. v

v 8. In a thermo-electric potentiometer, the combination with a plurality of thermo-couples constituting a thermoelectric source of potential, of a thermal. junction maintained at substantially the temperature of the air, a second thermal junction the temperature of which is to be determined, and means for determining the difi'erence ill temperature between the air second thermal junction by comparing the thermal-electromotive -lc'orce generated tween the same to the thermal electromotive force of the said plurality of thermocouples. 9. In an electricalmeasuring instrument, the. combination with a pluralityc't thermocouples arranged in a series having a predetermined thermo-electromotive force between the adjacentcold junction of two stantially at the temperature ofthe air, a hot junction of two dissimilar metals the temperature or which is to be determined, an electroresponsive device, and means for connecting the said hot and cold junctions to the said series of thermocouples to determine the difi'erence in temperature hetWeen the hot andtcold junctions.

16. in potentiometer, the combination with a source of thermoelectric potential of thermal junctio'h and the junctions thereof, of a dissimilar metals sub-' a thermo-couple comprising a junction maintained at substantially the temperature of the air and a hot junction. the temperature of which is to be determined, and means for connecting" the said thermo-couple to such parts of said'source of thermoelectric potential that no current will traverse the cir cuit thus formed. I

11. A-potentiometer comprising a plural ity of thermo-couples constituting a potentiometer conductor having points of predetermined potential and a thermocouple having one junction maintained at substantially the temperature of the air and a second junction the temperature of whichis to be determined, said thermo-couple being connected to such part of said potentiometer conductor that no current traverses the circuit thus constituted.

12' A potentiometercomprising a plurality of thermo-couples constituting a potentiometer conductor, a thermo-couple having one junction maintained at substantially air temperature and one j unctionat a temperature that is to be determined and a galvanometer, the galvanometer and the said thermo-couple being so connected in circuit With such part of the said potentiometer conductor that no current -traverses the galvanometer.

1.8. A. potentiometer comprising a pinrality of thermo-couples constituting a po-.

tentiometer conductor a thermo-couple having one junction maintained at substantially the temperature of the air and one junction at a temperature that is to be determined, a galvanometer, means for-connecting the air junction to the point on the potentiometer conductor that represents the air temperature and means for connecting the galvanometer between the hot junction and a sec end point on the potentiometer conductor that represents the temperature of the said hot junction. I

In testimony .WllGI'GOLl', I have hereunto subscribed my name this 24th day of Dee, 1914.

WIS W. ounce.

Witnesses: I

' B. B. Hines,

M. C. Mesa. 

